The exemplary embodiment relates to micro-electromechanical systems. It finds particular application in connection with a projection device comprising an array of independently addressable Fabry-Perot membranes and will be described with particular reference thereto.
Flat panel displays, such as liquid crystal displays (LCD) are widely used in a variety of applications, including watches, cell phones, and television displays. These displays rely on the combination of light of three primary colors to achieve a range of colors. The range and intensities of the colors which can be achieved with LCDs are often limited. The challenge is still in displaying rich chromatic colors at high resolution and at low power consumption.
Projection systems have the advantage that they are unobtrusive when turned off, since they can be smaller than a paperback book and can be mounted out of the way, on a ceiling or wall. Their size also makes them very portable. LCD and micro-electromechanical (MEMS)-based projectors are commonly used for business and home theater projection systems. In an LCD projector, light is sent through a layer of liquid crystals that either block or pass light by changing their polarization in response to an applied voltage. The color comes from red, green, or blue color filters placed in a grid that correspond to each of the three subpixels that make up a full pixel. MEMS-based projectors typically use an array of mirrors to reflect light onto the screen or shunt it away, with the color coming from a spinning color wheel that the light passes through, using the timing of the mirror movements to determine how much of each color will be shown on the screen. To create high definition images, a large number of mirrors are required to be individually operable, typically of the order of about a half to one million mirrors. The use of the color wheel limits the saturation of any one color, since its maximum duty cycle can only be 33% (assuming three colors). The color gamut of these two methods is limited to colors inside the triangle in the chromaticity diagram defined by the three filters. Thus the projectors cannot display colors of higher chroma than that of their filters, which excludes about half of the colors that the human eye can see. Additionally, since both systems require combinations of RGB (geographically separated or rapidly cycled in time) to create different colors within the visible range, the range of colors is limited.